CLAS physics database search results Measurement E151M2167 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.35 282 -0.748 0.748 0.062 0.45 282 -0.3447 0.7143 0.039 0.45 294 -0.525 0.7086 0.0485 0.55 282 -0.3686 0.6761 0.0402 0.75 66 -0.0981 0.6355 0.0308 0.75 78 -0.7798 0.6248 0.064 0.75 270 -1.3042 0.6227 0.0992 0.75 282 0.0695 0.7396 0.0304 0.85 66 1.2305 0.6403 0.0941 0.85 90 0.6327 0.7067 0.0548